.beta.-lactam antibiotics are widely used in the treatment of all kinds of bacterial infections. Representatives of the different groups (penicillins, cephalosporins etc.) of the said antibiotics have shown to be active or oral administration. Although an anhydrous form, hydrates, solvates, salts and esters of the .beta.-lactam antibiotics have been prepared, large differences in stability between the various forms of those antibiotics have been observed. For this reason flucloxacillin is commercially available only as the sodium salt, the anhydrous form of ampicillin is most preferred and the form of amoxicillin currently in use if the trihydrate. On the other hand other .beta.-lactam antibiotics have appeared to be stable in more than one form: e.g. phenoxymethylpenicillin is commercially available as the free acid, as various salts (calcium, sodium, potassium) and as an ester. However, on oral administration only the potassium salt has shown the best bioavailability. A person, who has to prepare a pharmaceutical dosage-form, containing a .beta.-lactam antibiotic, thus cannot always avail of that chemical form, which he would prefer in view of solubility and organoleptic properties.
Generally, if a quick onset of action of a drug from a solid dosage-form, such as a tablet, is aimed at, the composition and the manufacturing method of such tablet will be carefully selected as to enable a fast disintegration of the tablet and a dissolution of the drug, when placed in an aqueous environment. EP-B-0200281 discloses fast-disintegrating tablets, containing an amphoteric .beta.-lactam antibiotic, 24-70 wt % of a first disintegrant, which may be microcrystalline cellulose, and a second disintegrant. The tablets are prepared by making a wet granulate, comprising the antibiotic compound without using a substantial amount of a wet granulation binding agent, blending the granulate with the disintegrants and other excipients and compressing the tabletting mixture. EP-B-0330284 discloses a process for the preparation of a pharmaceutical granulate by granulating a drug having a solubility in water of less than 10 wt % and 20-100 wt % of microcrystalline cellulose with water without using a substantial amount of a wet granulation binding agent. From a granulate, obtained in this way, fast-disintegrating tablets, containing e.g. phenoxymethylpenicillin (as the acid) can be prepared. DE-A-2551249 discloses tablets, containing the water soluble .beta.-lactam antibiotic phenoxymethylpenicillin potassium. Although the inventors state that they have solved the problem of making fast-disintegrating tablets containing a high amount of a water soluble drug by using two different granulates (one containing phenoxymethylpenicillin potassium and a disintegrant and the other one containing a disintegrant only), the tablets are said to disintegrate in water and artificial gastric juice only after several minutes. In Example 2 of DE-A-2551249 tablets, containing 93 wt % of phenoxymethylpenicillin potassium and 3.5 wt % of maize starch, are disclosed. The tablets are said to disintegrate in water and artificial gastric juice after not more than 5-6 minutes. NL-A-6911804 discloses effervescent tablets, containing a water soluble .beta.-lactam antibiotic. Although this type of tablets should dissolve in water within a few minutes, they are not suitable for oral administration without dissolving the tablets in water first. FR-A-2320731 discloses fast-disintegrating capsules, containing an orally administrable penicillin or cephalosporin, including hydrates and salts thereof, and 1-8 wt % of cross-linked polyvinylpyrrolidone. The disintegration time of such capsules, containing amoxicillin trihydrate and ampicillin trihydrate, according to the only examples shown, was between 2 and 3.5 minutes. The best result was obtained, using amoxicillin trihydrate as the antibiotic and 3 wt % of intragranular cross-linked polyvinylpyrrolidone.
Another problem associated with oral dosage-forms, containing .beta.-lactam antibiotics, relates to the taste of the same compounds. It has appeared to be very difficult to mask the bad taste (acid or salty and bitter) of the antibiotics in order to provide an acceptable dosage-form for the patients, in particular children. Often large amounts of sugars or related polyhydroxy compounds, sweetening agents and flavours have to be used.
Although water soluble .beta.-lactam antibiotics are used for the treatment of infections already for many decades, there still is a demand for pharmaceutically acceptable quickly dispersible dosage-forms for oral administration, in particular tablets, which can be swallowed as a whole or taken as a suspension, obtained after dispersing the dosage-form in water. The dosage-forms at the same time should have an acceptable taste and/or after-taste, to be arrived at preferably without using substantial amounts of sugars and sodium-containing sweetening agents.